Chapter 7.8

Question 1

Although our genome includes approximately 25,000 protein encoding genes, our cells can produce some 400000 different proteins.

How can so few genes specify so many proteins

Answer 1

1. INTRONS: by removing different combinations of introns from mRNA molecule, a cell can produce several proteins from one gene

Question 2

What is the function of the 98.5 % of our genome that does not encode protein

Answer 2

1. some are regulatory ( e.g. Enhancers that control gene expression
2. much is transcribed to rRNA, tRNA, & microRNA
3. chromosomes also contain pseudogenes that are not able to be translated
4. TRANSPOSON: The human geneome is riddled with highly repetitive squences that have no known function. The most abundant type are TRANSPOSON ( these moveable pieces of Dna make up 45% of the human geneome
5. TANDEM REPEATS: ( AKA SATELITE DNA)

found in silent Dna, consist of one or more bases repeated several times

Question 3

PSEUDOGENE

Answer 3

DNA sequences that are very similarto protein encoding genes and that are transcribed but whose mRNA is not translated into protein

Question 4

How can the number of proteins encoded in DNA exceed the number of genes in the genome?

Answer 4

The 25,000 or so genes can make 400,000 proteins in part by changing which introns are removed prior to splicing together the mRNA.

Question 5

List some functions of the 98.5% of the human genome that does not specify protein

Answer 5

Some of the 98.5% of the human genome that does not code for protein encodes rRNA, tRNA, and regulatory sequences that control gene expression. It also contains pseudogenes that may be remnants of non-functional DNA that encoded proteins in our ancestors; transposons (transposable elements) that jumped from bacteria and viruses to humans; and tandem repeats of DNA sequences in telomeres, centromeres, and on the Y chromosome.